AI Writing With Dashes: Set the Punctuation Style You Want

AI writing uses dashes heavily: em dashes appear where a comma, a semicolon, or two shorter sentences would be clearer. If the output does not match your style, the fix is to state your punctuation preference explicitly in the prompt rather than editing each draft by hand.

Tools like fenbs let you save the approved punctuation style rules as a reusable prompt so any AI app you connect reads them before writing, not after.

Why AI writing overuses dashes

Dashes in AI writing appear most often as a way to add a qualification or a restatement mid-sentence. They signal informality and energy in the training data, so the model reaches for them when it wants to sound engaged rather than flat. The result is a style that reads as breathless rather than precise.

The pattern is common enough that "avoid em dashes" has become a shorthand for "make the AI writing sound less like AI." That is not quite right: the problem is unearned punctuation, and the solution is replacing it with structure rather than just removing it.

En dashes and hyphens are less common problems in AI prose, but if your style also prohibits mid-sentence en dashes, add that as a separate rule. Combined, "No em dashes: split the sentence or use a comma" and "En dashes for ranges only" cover most cases where AI punctuation departs from plain prose.

How to set your punctuation preference

Add a punctuation rule to your style instruction before the AI writes. Name the patterns you want to avoid and what to use instead:

• "Do not use em dashes. If a sentence contains an em dash, split it into two sentences or use a comma."
• "Use en dashes only for ranges (pages 12-15, 2020-2026). Do not use them mid-sentence."
• "Use commas for non-essential clauses, not dashes."
• "If a sentence has more than one dash, rewrite it."

The "rewrite it" rule is more effective than "avoid it." Asking the AI to avoid dashes produces fewer dashes; asking it to rewrite any sentence that contains one forces a structural decision about what the sentence is actually saying.

Prompts for revising existing drafts

To revise a draft that already overuses dashes, use a targeted revision prompt rather than asking for a general edit:

Revise the following draft.
Find every em dash and replace it using one of these options:
- Split the sentence into two shorter sentences.
- Replace the dash with a comma.
- Restructure the sentence to remove the need for the dash.

Do not change any other punctuation or sentence structure.
List every change you made.

[Paste draft here]

The "list every change" instruction makes the revision traceable. You can review each replacement and reject the ones where the original dash was actually the right choice.

Testing the instruction

Ask the AI to write a short paragraph on any topic with the punctuation rule in place. Count the dashes. If there are still dashes, check whether the rule was applied or ignored. A rule that is stated once at the top of a long instruction sometimes loses effect; move it closer to the writing task or restate it just before the content request.

Test on a few different topics. Dash use tends to creep back in on technical or explanatory content where the AI wants to add a qualification. If that is where the rule breaks, add: "Even when adding a qualification, use a comma rather than a dash."

A useful diagnostic before writing the instruction: paste a two-hundred-word sample of recent AI output and ask the model to mark every dash and classify it as necessary (marking a sharp turn or a strong appositive) or replaceable (adding a qualification that a comma could carry). Most dashes in typical AI prose fall into the replaceable category. Running this classification once makes the scale of the problem visible before you write the rule.

How to do this with fenbs

1. Create a free account and add a project for the content work.
2. Add the punctuation rules to Skills and prompts in fenbs alongside the rest of your style instruction.
3. After testing, record which rule version produced consistent results in Lessons learned.
4. Connect your AI app over MCP from Integrations so it reads the current style rules at the start of each writing session.

When dashes are the right choice

Not every dash is wrong. An em dash can mark a sharp turn in a sentence or a strong appositive, and using it deliberately once or twice in a piece is different from using it in every other sentence. The goal is a preference you can state clearly, not a blanket prohibition.

If your style allows one dash per paragraph for deliberate effect, add that as a rule: "One em dash per paragraph is permitted for emphasis; otherwise, restructure." A rule you can test is more useful than one the AI interprets loosely.

Dash overuse is often a symptom of a sentence that relies on mid-sentence interruptions instead of sequencing its ideas. A sentence that uses a dash to add a qualifier usually has a subject that is not doing enough work to carry the sentence alone. The revision prompt that forces a sentence split rather than a comma replacement is useful precisely because it makes that underlying structure visible. The result is not just fewer dashes but clearer sentences throughout.